Although little is known currently to explain the familial clustering of breast cancer, a large amount of susceptible genes and SNPs of this disease have been recently reported, including the well-known high breast cancer risk in BRCA1 and BRCA2 mutation carriers as well as the risk for breast cancer in certain rare syndromes caused by mutations in TP53, STK11, PTEN, CDH1, NF1 or NBN [70]. This evidence concerns the gene STK11 and breast cancer.